桂西地区不同林龄栎类群落的生物量及其分配格局

根据5个不同林龄15块1000m2样地的调查资料,利用15株不同林龄和径阶的栎类样木数据,建立以胸径平方乘以树高(D2H)为单变量的生物量估算模型。采用样木回归分析法(乔木层)和样方收获法(灌木层、草本层、地上凋落物)获取不同林龄栎类的生物量,并分析了其组成、分配特征及不同林龄生物量的变化趋势。结果表明:栎类林分的总生物量随林龄而增加,5个不同林龄的生物量分别为73.67Mg/hm2、127.47Mg/hm2、149.93Mg/hm2、169.90Mg/hm2、200.65Mg/hm2,其中活体植物的贡献达95.58%以上,地上凋落物的总量不超过4.42%；生物量的层次分配方面乔木层占绝对优势,占93.66%-98.68%,其次为地上凋落物,占1.02%-4.42%,灌木层和草本层生物量较小,分别占0.20%-2.13%和0.03%-0.27%,均随林龄的增加呈递减趋势；乔木层器官分配以干所占比例最高,占46.64%-80.78%,且随林龄而增加,枝、叶、根分别占11.61%-36.80%、1.00%-4.85%和6.61%-11.71%,均随林龄而下降；灌木层器官分配以枝所占比例最高,为32.50%-69.07%,叶和根分别占12.89%-25.00%和18.04%-42.50%；不同林龄栎类草本层生物量大小与林龄成反比例关系,地上部分的生物量大于地下部分的生物量。随着林龄的增加,凋落物呈现升→降→升的趋势。以上研究结果表明,林龄可以影响桂西地区栎类的生物量和分配格局。

Oak Biomass and Its Allocation at Different Stand Ages in West of Guangxi, China

Biomass estimation model for single variable (square of high tree diameter multiply by height at breast, D2H) was established based on 15oak wood of different age, size order and 15pieces of sample survey data of 1000m2at five different forest ages. We obtained oak biomass of different forest ages by using regression analysis (tree layer) and the method of quadrat harvest (shrub layer, herb layer, litter on the ground), and analyzed the composition, distribution characteristics and change tendency of different forest age biomass. The results showed that the oak biomass increased with forest age and biomass of five different age were 73.67Mg/hm2,7.47Mg/hm2,9.93Mg/hm2,9.90Mg/hm2and 200.65Mg/hm2respectively. In total biomass, living plants accounted more than 95.58% and that of litter less than 4.42%. As for level distribution of biomass, the total biomass was dominated tree layer (accounting for 93.66% - 98.68% of total biomass). Then, it was followed by litter on the ground (accounting for 1.02% - 4.42%), and the shrub layer and herb layer biomass, which accounting for 0.20% - 2.13% and 0.03% - 2.13% respectively. As for organ allocation at tree layer, stem accounted for 46.64% - 80.78% of oak biomass and increases with forest age, while branch, leaf, root for 11.61%- 36.80% , 1.00%- 4.85% and 6.61% - 11.71% respectively. At the shrub layer, branch was highest, which accounting for 32.50%- 69.07% of shrub biomass, and leaf and root accounted for 12.89% - 25.00% and 18.04% - 42.50% respectively. As for herb layer, the biomass was inversed for forest age and above biomass was greater than that of underground. With the increasing of forest age, litter biomass showed the change trend of up - down - up. Briefly, it was implied that the biomass and allocation pattern of Oak could be affected by stand ages in west of Guangxi, China.